New Tsallis Holographic Energy in Rastall Theory Constrains Cosmological Parameters with DESI and PantheonPlus Data

The accelerating expansion of the universe drives research into the nature of dark energy, and a new study explores a compelling candidate using a combination of theoretical frameworks, namely New Tsallis holographic energy and Rastall gravity. N. Sadeghnezhad, R. Jalalzadeh, and Z. Davari, alongside B. Afshar, investigated this combined model, placing observational constraints on its parameters using data from the DESI BAO, PantheonPlus supernovae, and Hubble parameter measurements. Their analysis reveals that this approach not only provides a dynamic alternative to the standard cosmological model, ΛCDM, but also offers predictions for the expansion rate at intermediate redshifts that align slightly better with current observations. Importantly, the team demonstrates that combining the unique energy density predicted by New Tsallis holographic energy with the modifications to gravity proposed by Rastall theory yields a plausible model that accurately reproduces the observed amount of dark energy in the universe, something New Tsallis holographic energy alone cannot achieve.

Their analysis reveals that this approach provides a dynamic alternative to the standard cosmological model, ΛCDM, and offers predictions for the expansion rate at intermediate redshifts that align slightly better with current observations. Many studies focus on resolving this tension by exploring alternative cosmological models, modified gravity theories, and improved statistical methods for analyzing observational data, utilizing data from DESI, Pantheon+, and various Hubble constant measurements. A significant portion of research is dedicated to Rastall gravity, a modified theory of gravity where the divergence of the energy-momentum tensor is not necessarily zero, explored as a potential explanation for dark energy and a way to alleviate the Hubble tension. Strong emphasis is placed on Bayesian statistical methods for cosmological parameter estimation, employing techniques like Markov Chain Monte Carlo (MCMC) for robustly estimating cosmological parameters and assessing model evidence.,.

Constraining Cosmological Parameters With Multiple Datasets

The study rigorously constrained cosmological parameters using a comprehensive dataset encompassing Type Ia supernovae from the PantheonPlus survey, Baryon Acoustic Oscillation data from DESI, Hubble parameter measurements, and Big Bang Nucleosynthesis constraints. Researchers employed not only the minimum chi-squared statistic but also the Bayesian evidence and the Akaike Information Criterion to assess model preference. The Bayesian evidence was estimated using the Truncated Harmonic Mean Estimator, a method that provides a stable approximation to the marginal likelihood. The results demonstrate that this model not only provides a dynamic dark energy framework but also yields predictions for the Hubble parameter that align slightly more closely with intermediate-redshift observations compared to the standard ΛCDM model. The team developed a cosmological model based on modified Friedmann equations incorporating the Rastall parameter, and subsequently derived expressions for key quantities such as the deceleration parameter and the redshift-scale factor relationship. Measurements confirm that the model’s parameters are consistent with current observational data, and the analysis establishes the allowable range for the Rastall parameter, finding it must fall within specific bounds determined by thermodynamic analysis and observational studies. By analyzing data from multiple sources, including supernova observations, baryon acoustic oscillations, and measurements of the Hubble parameter, scientists successfully constrained key cosmological parameters within this new framework. The results demonstrate that this combined model accurately reproduces the observed cosmic expansion history and yields values for fundamental quantities, such as the Hubble constant and the age of the universe, consistent with current observational expectations. Importantly, the model not only provides a viable alternative to the standard cosmological model, ΛCDM, but also offers subtle deviations at intermediate redshifts, potentially offering observational signatures to distinguish it from the standard scenario.

The study confirms previous constraints on the Rastall parameter, indicating that only minor departures from standard energy conservation are required, and finds evidence suggesting that non-extensive statistical effects may play a significant role in the behavior of dark energy. The combination of the Rastall term and the new dark energy formulation proves crucial, successfully mimicking the current value of the dark energy density parameter reported in the ΛCDM model, something the new dark energy alone could not achieve. The authors acknowledge that the analysis focuses on background-level observations and does not include perturbations, representing a limitation for future work, and suggest that further research should investigate the model’s predictions for cosmic structure formation and explore the implications of incorporating early universe data to refine the constraints on the model’s parameters. This work establishes a promising new framework for understanding the accelerating expansion of the universe and provides a foundation for future investigations into the nature of dark energy.